You might try using an adjustable wrench that will fit the flats and see if you can get it to turn back an forth to loosen it up. Normally you would use blue locktite on those type screws and shouldn't really need heat to loosten it up unless for some reason they used red locktite, but then I doubt you would have been able to loosen the set screws without heat. Were the set screws really tight or did they come out fairly easily?